Noncontact Atomic Force Microscopy - Yale School of Engineering ...

2-Dimensional growth of phenylenediboronic acid assisted by
H-bonding
We-1510
R. Pawlak, L. Nony, F. Bocquet, M. Sassi, V. Oison, J.-M. Debierre, Ch. Loppacher,
and L. Porte
IM2NP, Aix-Marseille Université, Avenue Escadrille Normandie-Niemen, F-13397 Marseille Cedex 20,
and CNRS, IM2NP (UMR 6242), F-13397 Marseille-Toulon, France
Christian.Loppacher@im2np.fr
Organic molecules are often synthesized in order to support the formation of selfassembled
nanostructures. In such a way, directed non-covalent [1] as well as covalent
interactions [2] have already been used to tune the size as well as the shape of molecular
assemblies. 1,4 Phenylenediboronic acids (C6H8B2O4, BDBA) are molecules which are
designed to engage in multiple interactions with neighbors via their –B(OH)2 groups,
either by hydrogen bonding or by covalent bonding (obtained by molecular dehydration).
In our work, we investigate the molecular growth of BDBA on the surface of singlecrystal
potassium chloride (KCl) as well as on highly oriented pyrolytic graphite (HOPG)
by means of noncontact atomic force microscopy (ncAFM). Other than on the surface of
Ag(111) BDBA does not form the honey-comb like covalent network [3], but rather
forms chains of hydrogen-bonded dimers, and the chains then associate by lateral
hydrogen bonding to create sheets [4]. The ncAFM results displayed in the figure below
show that extended and well organized monolayers of BDBA are formed on KCl. The
observed structure fits very well to the one observed in crystals where the benzene ring is
tilted by ~ 40° with respect to the mean plane of the sheet [4]. Interestingly, this structure
seems to be very stable since it is also observed on the surface of HOPG. Experimental
results are discussed in respect with structural models as well as calculations of the
reaction path for the formation of covalent networks.
Figure 1: 0.5 ML of BDBA adsorbed on KCl imaged by ncAFM. Large monolayer islands are
formed which show the formation of sheets similar to the ones observed in single crystals.
[1] T. Yokoyama et al., Nature 413, 619 (2001).
[2] L. Grill et al., Nature Nanotechnology 2, 687 (2007)
[3] N. Zwaneveld et al., JACS 190, 6678 (2008)
[4] P. Rodriguez-Cuematzi et al., Acta Cryst. E60, o1315 (2004)
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